The present invention relates to a movable reflector type vehicle headlamp where a reflector to which a discharge bulb is fitted is tiltably supported by an aiming mechanism. More particularly, it relates to a vehicle headlamp in which a ballast circuit unit that allows the discharge bulb to discharge stably is housed in a lamp body.
As shown in FIG. 9, in a conventional vehicle headlamp of this type, a reflector unit 2, which integrates a pair of right and left reflectors 3, 4, is housed in a lamp body 1. A discharge bulb 5 is fitted in the reflector 3 and an incandescent bulb 6 is fitted in the other reflector 4. An aiming mechanism E including one aiming pivot point a and two aiming screws b, c is interposed between the reflector unit 2 and a lamp body back surface wall 1a. The reflector unit 2 is tiltably and adjustably provided with respect to the lamp body 1. Reference numerals Lx1, Ly1 denote a horizontal tilting axis and a vertical tilting axis of the reflector unit 2.
The aiming pivot point a is disposed between the right and left reflectors 3, 4 so that the reflector unit 2 can be tilted by rotating the lateral direction aiming screw c.
A reference numeral 7 denotes a ballast circuit unit that allows the discharge bulb to discharge. It is disposed on an inside of a lamp body bottom surface wall 1b. An output cord 7a from the ballast circuit unit 7 is connected to a back end portion of the discharge bulb 5.
However, because the heavy ballast circuit unit 7 is provided immediately below the discharge bulb 5, it may vibrate because of vehicular motion. Namely, because the center of gravity G1 of the headlamp excluding the ballast circuit unit 7 is far away from the center of gravity G2 of the ballast circuit unit 7 alone, the entire headlamp may vibrate from the motion of the vehicle, resulting in abnormal noise, asymmetric friction, and misaligned optical axis and the like.
An object of the present invention is to provide a vehicle headlamp that does not vibrate by locating the center of gravity of the ballast circuit unit housed in the lamp body near the center of gravity of the lamp fixture.
To achieve the above object, a pair of first and second reflectors are disposed in a lamp body, a discharge bulb is fitted in at least one of the reflectors, and a ballast circuit unit that allows the discharge bulb to discharge stably is disposed at a lower portion inside the lamp body. In the vehicle headlamp, the pair of first and second reflectors are offset in a vertical direction so that a bottom surface of a first reflector is located at a higher position than a bottom surface of a second reflector that is adjacent to the first reflector. The first reflector is offset with respect to the second reflector in a fore-and-aft direction so that the first reflector is located behind the second reflector. The ballast circuit unit is disposed in an enlarged space that extends from below the first reflector to a back of the second reflector in the lamp body.
A first space large enough to house therein the ballast circuit unit is provided below the first reflector that is offset upward. However, even if the ballast circuit unit is disposed immediately below the first reflector, the center of gravity of the ballast circuit would not be aligned with the center of gravity of the headlamp excluding the ballast circuit unit.
Therefore, the first reflector is offset behind the second reflector (the second reflector is offset ahead of the first reflector) to free a side (on the second reflector side) of the first space below the first reflector, and the ballast circuit unit is disposed in a space including this freed space.
Because the second reflector is disposed ahead of the first reflector, a second space is formed that laterally communicates with the first space at the back of the second reflector. In other words, the first space below the first reflector is laterally enlarged by a space equivalent to the second space behind the second reflector.
If the ballast circuit unit is disposed to extend over the first space and the second space that communicate with each other, the center of gravity of the ballast circuit unit alone is made near the center of gravity of the headlamp excluding the ballast circuit unit.
In another embodiment of the invention, the first and the second reflectors of the headlamp are integrated together to form a reflector unit and are tiltably supported by an aiming mechanism interposed between the lamp body and the reflector unit. The ballast circuit unit is housed in a ballast housing chamber defined by a ballast cover attached to the lamp body and a lamp body bottom surface wall. The ballast cover is provided with an aiming pivot point of the aiming mechanism.
Because the right and left reflectors (the first and the second reflectors) are integrally formed as the reflector unit, the construction of the aiming mechanism is made simple.
Further, because the construction of the aiming mechanism is simple, interferences can be avoided between the aiming mechanism and the ballast cover that forms the ballast housing chamber.
In addition, because the ballast circuit unit is housed in the ballast housing chamber, the ballast circuit unit does not vibrate.
Also, because the right and left reflectors are integrated as the reflector unit, a load is made greater at a reflector unit side acting on a portion surrounding the aiming pivot point. However, because the aiming pivot point is provided between the ballast cover (located ahead of the lamp body back surface wall) and the reflector unit, the distance between members where the aiming pivot point is interposed is shorter than when the aiming pivot point is provided between the lamp body back surface wall and the reflector unit. Thus, the length of a leg formed on the reflector unit side to support a ball joint or other member that forms the aiming pivot point is made shorter. Therefore, the rigidity of the leg as a portion surrounding the aiming pivot point is enhanced.